ph meter with temperature compensated large range scale and small range expanded scale

Claim 1

A PH METER INCLUDING A VOLTAGE RESPONSIVE INSTRUMENT HAVING A RELATIVELY LARGE RANGE MAIN SCALE AND A RELATIVELY SMALL RANGE EXPANDED SCALE WHICH CAN BE USED TO READ OVER DIFFERENT PARTS OF THE MAIN SCALE; MEANS FOR CHANGING OVER THE INSTRUMENT TO READ EITHER ON ITS MAIN SCALE OR ON ITS EXPANDED SCALE; TEMPERATURE COMPENSATED AMPLIFIER MEANS FOR APPLYING TO SAID INSTRUMENT A PH REPRESENTATIVE VOLTAGE WHICH, WHEN THE MAIN SCALE IS IN USE, IS APPROPRIATE TO THAT SCALE AND IS FULLY TEMPERATURE COMPENSATED, INCLUDING BOTH SLOPE AND INITIAL COMPENSATION APPROPRIATE TO THAT SCALE; AND MEANS OPERABLE WHEN THE EXPANDED SCALE IS IN USE FOR CHANGING THE VOLTAGE FED TO THE INSTRUMENT TO A VALUE APPROPRIATE TO THE EXPANDED SCALE AND SIMULTANEOUSLY ALTERING THE TEMPERATURE COMPENSATION, BOTH AS RESPECTS SLOPE COMPENSATION AND INITIAL COMPENSATION TO MAKE THE CHANGED OVERALL TEMPERATURE COMPENSATION APPROPRIATE TO THE EXPANDED SCALE, THE LAST MENTIONED MEANS INCLUDING MEANS, GANG CONTROLLED WITH THE MEANS FOR CHANGING THE PART OF THE MAIN SCALE COVERED BY THE EXPANDED SCALE, FOR VARYING THE INITIAL TEMPERATURE COMPENSATION.